You're right, in that there is a tension between systems behaving equally and equitably, and that either one can be seen as "bias". (Although there can of course be systems that by design behave neither equally nor equitably, whether intentional or not.)

I think the "algorithm has bias" type of headlines proliferate because there's a common misconception that algorithms are somehow "objective". See for example Ryan Saavedra implying algorithms can't be racist because they're "driven by math": https://twitter.com/realsaavedra/status/1087627739861897216?...